Tuesday, September 12, 2017

Securing Privileged Access for the AD Admin – Part 1

Hello again, my name is still David
Loder, and I’m still a PFE out of Detroit, Michigan. I have a new confession to make.I like cat videos.Your end users like cat videos.You may like cat videos yourself.Microsoft will even help you find cat
videos.Unfortunately, cat videos
may have it out for you and your environment.How do you keep your environment secure when malicious cat videos are
out there, waiting to pounce?

Microsoft has a significant amount of published guidance
around Securing Privileged Access (SPA), Privileged Access Workstations and the Administrative Tier Model.My fellow PFEs have also contributed their
own great thoughts around these topics.Go browse through our Security
tagged posts to get easy access to them.As for myself, I was staff IT in the security department for a large,
global corporation, prior to joining Microsoft, where we operated in a tiered
administrative model and had implemented many, though not all, of the defenses
highlighted in the SPA roadmap.So I’d
like to share my perspective on the items in the roadmap and the practical
implications from an Active Directory Administrator point of view.

But first a caveat for this series of articles.I love the SPA roadmap.I espouse its virtues to all my customers and
anyone else who will listen.But there
are times where the SPA roadmap takes a big step, and I know it can sometimes
be difficult to get the people in charge to agree to a big step.In all the cases where I point this out it is
possible to take a smaller step by limiting the scope by focusing solely on
AD.I have a different purpose for this
series of articles than the SPA roadmap itself.I want you to actually implement the guidance.That’s a shocking statement, I know.Despite all the guidance, I still walk into
environments that haven’t implemented a single piece of this guidance.Maybe they don’t know this guidance
exists.Maybe they think they aren’t a
target.Maybe they think the guidance
doesn’t apply to them.My hope with this
series is that a few more people know about the guidance, understand why they
should care and have an easier time convincing others in their organization
that the roadmap guidance should be implemented.Security is a journey.Through no fault of your own, the rules have
changed.What you did to secure your
environment yesterday is no longer sufficient for today’s reality.So, let’s get started.

Separate Admin Account for Admin Tasks

This is an easy one, right?Nothing about this guidance is new.It ranks right up there with not browsing the Internet from a
server.But I am constantly seeing environments
where normal user accounts, which have a mailbox and browse the Internet for
cat videos, are also in the Domain Admins group.Stop this.Stop this now.You need a
separate credential for administrative tasks.Come up with a naming convention and a process to get an admin account
for anyone who does admin work.

I know some of you are smiling and thinking to yourself ‘of
course we do this; the admins get their ADM_username accounts for performing
admin work’ (or their $username or their username.admin or whatever convention
you use).But, have you made the
correlation between tiering and admin
accounts?To fully implement the
guidance, a user with admin rights must have a separate admin account per tier!

Let that sink in for a minute. In a three-tier model, the AD
Admins may require four separate credentials: user (non-privileged), tier-2
(workstation) admin, tier-1 (server) admin and tier-0 (security infrastructure)
admin. This guidance is designed to avoid having a credential that has admin
rights in multiple tiers. This helps prevent a pass-the-hash
attack from elevating from a lower tier to a higher tier.

Now for the practical part.Yes, this gets hard to do.You
may have processes in place that will get a second credential to admin users,
but it wasn’t designed to get them four.Maybe you have clear separation between server admins and workstation
admins, so no one will need all four.We
want the guidance to be actionable and most importantly to protect tier-0.Guidance that isn’t followed because it is
too burdensome isn’t valuable. At a minimum, your AD Admins should have three
accounts: user, admin, tier-0 admin.And
your goal is to minimize the scope of tier-0.Tier-0 admin accounts should only be managed by other tier-0 admin
accounts and not by a tier-1 system.Please don’t have your normal Identity Management (IdM) system try to manage AD Admin accounts.Because you’ll either fight with AdminSDHolder or you’ll have to grant your IdM system Domain
Admin rights and neither of those is a good choice.

Tier 0 – Direct Control of enterprise identities
in the environment. Tier 0 includes accounts, groups, and other assets that
have direct or indirect administrative control of the Active Directory forest,
domains, or domain controllers, and all the assets in it. The security
sensitivity of all tier 0 assets is equivalent as they are all effectively in
control of each other.

Control of a
tier-0 system means control of the entire environment.The very nature of Active Directory means
there should be at least two tiers in the environment: AD itself, and
everything else.Splitting between tiers
isn’t a hard and fast line.The tiering
is there to provide a security boundary that is supposed to be difficult to
cross.You can certainly have user
workstations that might need to be treated more like a tier-1 system because of
the value they hold.The point is that
your organization must decide which security boundaries should exist that
define the tiers and the systems contained within those tiers.This is especially true of tier-0.

At a minimum
tier-0 will contain Active Directory; specifically, the writeable Domain
Controllers and the AD Admin credentials.Those credentials are any account that is a member of Domain Admins,
Enterprise Admins, Builtin Administrators, etc.These groups are all equivalent.Don’t think being Builtin Administrator is somehow more secure or
different than being Domain Admin.

What else is tier-0? Look in your AD Admin groups.Every account in them is a tier-0
credential.Ideally, they are
credentials only for people and they are unique to the management of AD
infrastructure, following a naming convention that distinguishes them from your
normal tier-1 admin accounts.In other
words, the tier-0 credentials that are members of the AD Admin groups must be
used for the sole purpose of managing AD infrastructure and for nothing else.

If you have service accounts in your AD Admin groups, those
service accounts are tier-0 credentials.The servers where those service accounts are used are tier-0
systems.Anyone who is administrator on
those servers has access to tier-0 credentials.Do you see how quickly this grows?While you may normally think of just AD as being tier-0, your tier-0
equivalency may be immense.In fact,
you may not have a tier-1 or tier-2 layer at all.It is possible that you are operating an
environment where everything is tier-0.

I will state again; the goal is to minimize tier-0.Your AD Admin groups should only have people
in them, not service accounts.Use the
delegation abilities within AD to grant those service accounts only the rights
they need.Yes, it may be hard work to
figure out what and where those rights are needed, but it’s the job that needs
to be done to keep things that should be tier-1 from being tier-0.

What else is tier-0? Are your DCs virtualized? If so your VM
admins are tier-0 admins.Your VM
platform is a tier-0 system. Your VM storage is a tier-0 system. Your storage
admins are tier-0 admins. Do you see how quickly this grows? Hyper-V in Windows
Server 2016 offers Shielded
VMs to mitigate this risk.

What else is tier-0? What additional services run on your
DCs? Which of those services are listening on the network and running as Local
System? Which of them report into some kind of management console to receive
instructions on what to do? Does that describe your SIEM agent, your anti-virus
agent, your asset management agent, your configuration management agent? Your SIEM
team has control over a tier-0 system.Your
SIEM is a tier-0 system.Your AV
platform is a tier-0 system. Your configuration platform is a tier-0 system. Do
you have a standard corporate image that you use for all servers, including the
servers that you will promote to become Domain Controllers? Everything added to
that image has the possibility of being a tier-0 system. Do you see how quickly
this grows?

What else is
tier-0?Is your IdM system tier-0?
Maybe. By our definition it should be since it has direct control of the
enterprise identities.What if it is
only delegated rights to a specific set of OUs and it doesn’t use an AD Admin
account to manage the users?If that
system is compromised is tier-0 compromised?The integrity of the AD infrastructure is still intact.It may no longer contain the user data you
wanted it to contain but you still have administrative control over AD and can more
easily recover.It that a bad day? Absolutely.
But you can still point to a security boundary that wasn’t crossed.A defense in-depth mindset would have more
boundaries to cross when possible.

Control over your tier-0 equivalencies is likely the hardest
part of the roadmap; which is why it practically shows up later in the
roadmap.But I wanted to discuss it up
front, as understanding the true nature of your own tier-0 definition is
paramount to being able to have successfully implemented the roadmap at the end
of the journey.

Now that we all
understand the impact of tier-0 equivalencies, how many credentials in your
enterprise (from both humans and service accounts) are tier-0 admins?Is it 5 or 100?How many do you want at that tier?5 or 100?Personally, I’d vote for 5.Keep
in mind that we’re focusing on credentials.This shouldn’t be a discussion that we trust, for example, the VM Admin
team less than the AD one.It’s that the
more credentials and systems that exist at tier-0, the more surface area we
have to consider in an assumed-compromised state.

As a personal
story from my previous life many years ago, the first time we had to integrate
a non-AD workload into tier-0, we thought the sky was falling and it was the
destruction of our security posture because a different team was suddenly
involved.It took me a while to
recognize that tier-0 doesn’t exclusively mean AD.Every organization will have a unique
combination of workloads and roles that will be their tier-0, and that’s
OK.What’s important is define the
boundary then make every workload and every person in tier-0 operate to the
same standard.

Once you and your
organization have made your decision about defining your intended tier-0
boundary, go make totally separate admin accounts for those that you want to
end up operating at tier-0.Yes,
managing three or four credentials is more difficult than one.But you’re the AD admin for your enterprise
and if you aren’t taking the lead in enabling this change, no one else will do so.If
you already have a separate admin account, but it’s crossing tier boundaries
(existing or planned), go get your third credential.Making use of the third is almost no
additional effort beyond a second credential.Here’s where you have one of those big step/small step decisions to
make.If having separate admin accounts
for everyone who does administration in your organization is too big of a
change to make all at once, start small with only those admins who manage
AD.Show everyone that the world doesn’t
end if you have to manage separate credentials for AD Admin purposes.

Ensure you have
proper procedures for creating and managing the new tier-0 admin
credentials.My first preference is to
manage them manually, outside of the scope of any IdM platform you have in
place, with proper, proactive scheduled reviews. Hopefully you’ve caught on to
the hints that managing tier-0 will be easier when it’s small.That allows manual management of tier-0
credentials to be successful.If you’re
in a more mature organization, then you can look to a dedicated tier-0 IdM
system that can manage these credentials.

To summarize this
post into a 30 second elevator speech:

1.Active
Directory Domain Controllers are tier-0 systems.

2.AD
Admin credentials are a tier-0 credentials.

3.Anywhere
that tier-0 credentials are used is a tier-0 system.

4.Anything
or anyone that has administrative control over any part of 1, 2 or 3 is also a
tier-0 credential/system.

5.Keeping
1, 2, 3 and 4 small makes tier-0 easier to manage and more secure.

That’s it for
now.The first step down the roadmap is
both incredibly simple and incredibly hard at the same time.I want to give you a break to allow the full
impact of the guidance to soak in.Check
back in next week, where we’ll continue our discussion of the roadmap.But please, go create your separate AD Admin
account right now.I shudder to think
you’ve been reading this with a browser running under AD Admin credentials, with
your cat videos playing in another tab.